The Doctor is summoned back to the planet Tigella, where the population
is divided along religious and scientific lines. Something is going
terribly wrong with Tigella's main power source, the Dodecahedron, but
the Savants are prevented from investigating by the zealous Deons. To
make matters worse, before the Doctor can solve the problem with the
Dodecahedron, he is accused of its theft. The true culprit is Meglos, a
shapeshifting Zolfa-Thuran, who intends to unleash the full might of the
Dodecahedron upon the universe.

Production

When Christopher H Bidmead became Doctor Who's script editor at
the end of 1979, he found himself scrambling to develop stories for the
programme's upcoming eighteenth season. Both he and producer John
Nathan-Turner were eager to bring new talent onto the show, and so one
of the first people Bidmead contacted was an actor he knew named Andrew
McCulloch. McCulloch, who had once starred in the police drama
Parkin's Patch, had formed a writing partnership with an actor
and journalist named John Flanagan, whose television appearances had
included The Sweeney. Together, Flanagan and McCulloch had
written a stage play and an unsuccessful television pilot called
Bricks Without Straw.

On February 25th, 1980, Flanagan and McCulloch were commissioned to
write a scene breakdown for an idea they had suggested called
Meglos. Nathan-Turner was unimpressed with an adventure that he
saw as just standard Doctor Who fare, but with time pressing,
Flanagan and McCulloch were contracted to provide full scripts on March
10th. Since the pair wrote quickly, it was decided that “The
Golden Star” -- as the adventure had now been renamed -- would be
the third story into production, coming after The
Leisure Hive and State Of Decay.
Unlike the latter, “The Golden Star” would not feature new
companion Adric, and so it was slotted as the second broadcast adventure
of Season Eighteen.

The name Brotadac was jokingly devised as an anagram of
“bad actor”

Serial 5Q went through a number of working titles, apparently including
“The Golden Pentangle”, “The Golden Pentagram”
and “The Last Sol-Fataran” before becoming “The Last
Zolfa-Thuran” by the end of April. Several of these names
reflected the evolving shape of the Dodecahedron, which was originally a
five-sided object (influencing the number of screens found on
Zolfa-Thura) rather than a twenty-sided object made up of pentagons.
Keen to inject more science into Flanagan and McCulloch's scripts,
Bidmead suggested the chronic hysteresis element, the terminology
derived from a loop-like phenomenon which arises in fields such as
electromagnetism. Meanwhile, Flanagan and McCulloch jokingly devised the
name Brotadac as an anagram of “bad actor”!

As with Peter Moffatt, who had directed State Of
Decay, Nathan-Turner chose a former colleague on All
Creatures Great And Small to direct Serial 5Q. This was Terence
Dudley, whose other credits included Doomwatch and
Survivors (both of which he also produced), Softly Softly
and Secret Army. Dudley was also a writer, and had been invited
to contribute to Doctor Who during its first season, although
nothing had come of this.

One of Dudley's friends was director Alvin Rakoff, whose wife,
Jacqueline Hill, was eager to resume her acting career after a long
absence spent rearing their children. Dudley agreed to cast Hill as Lexa
in “The Last Zolfa-Thuran” -- much to the approval of
Nathan-Turner, who was aware that one of Hill's most successful roles
prior to her retirement had been as Barbara Wright, one of the original
Doctor Who companions in the mid-Sixties. This marked the only
time that a series regular would later return to Doctor Who as a
new character. In Flanagan and McCulloch's original storyline, Lexa had
simply vanished from the action once she had served her purpose within
the narrative. Bidmead suggested her act of self-sacrifice as a more
dramatic end for the character.

Although Flanagan and McCulloch had hoped that many of the scenes on
Tigella and Zolfa-Thura would be achieved on location, Nathan-Turner
decided that Serial 5Q represented an opportunity to save money, and so
it was recorded entirely in the studio. The first session was held from
June 25th to 27th in BBC Television Centre Studio 8, during which Dudley
opted to record all of the Tigella scenes. At this point, Tom Baker had
finally begun to slowly recover from the illness which had plagued him
throughout the season to date. Meanwhile, by this time the adventure's
title had reverted back to the writers' original choice:
Meglos.

The Scene-Sync process was offered for use in Meglos as a test case, free of charge

The second set of studio days took place in TC3 and spanned July 10th to
12th, concentrating on all of the sequences on Zolfa-Thura. Models shots
were completed on the 11th, while taping on the 12th also included an
additional scene in the Tigellan jungle and material aboard the Gaztak
spaceship. A major element of recording on the middle day involved a new
process called Scene-Sync. A more advanced version of the ChromaKey (or
Colour Separation Overlay) technique used on Doctor Who
throughout the Seventies, Scene-Sync allowed greater camera mobility
than had previously been the case. However, it was an unproven process
at the BBC and so it was offered to Doctor Who for use on
Meglos, free of charge, as a test case. Dudley's implementation
of Scene-Sync for some of the Zolfa-Thuran sequences was judged to be a
success.

Meglos was Flanagan and McCulloch's only contribution to
Doctor Who although another story of theirs, “Project
Zeta-Sigma”, was at one point planned to open Season Nineteen.
Following its abandonment, the pair went on to write for programmes such
as Robin Of Sherwood, Peak Practise and Heartbeat.
McCulloch also continued acting, notching appearances in shows like
The Young Indiana Jones Chronicles.

Meanwhile, on August 29th, popular waxworks museum Madame Tussauds
unveiled a display called The Doctor Who Experience to celebrate
the debut of the programme's eighteenth season. The exhibit included a
waxwork of Tom Baker, in costume as the Fourth Doctor. Following the
broadcast of Meglos, this was joined by a statue of the Doctor's
Meglos doppelganger, making Baker the first person to be simultaneously
represented with two different waxworks at the famed gallery.